Odour modifiers

Friction agents Odour modifiers Plasticisers Smoke suppressants... 

The distillates consisted principally of camphor the loots aloue yielded an oil, which possessed an odour reminisceut at the same time of camphor and of lemous. Afterwards numerous eijjcrlmenls were earned ont with various distilling apparatus which hod been portly modified. 

They stated that the influence of these groups is not easily deflnahle with exactness and that the presence of other groups may modify profoundly their effect, even so far as entirely to suppress the odour. 

The methyl group, para to the isopropyl, modifies, but is not essential for, the production of the lemon odour since A nor-menthadiene is verv like lemons in odour. 

It should also be noted that the lemon odour is not confined to the para isomers, as it is even more pronounced in several of the ortho and meta bodies, although generally modified. 

Ethyl Malonate.—Ethyl malonate is not a member of the parafiinoid acid esters, but is sufficiently nearly related to this series to be included here as a matter of convenience. It is of considerable value in modifying flower odours, having a more or less characteristic apple odour, but of a much sweeter type than the valerianic ester perfume. It is an oil of specific gravity 1 068, and boils at 198°. 

Ethyl Nonylate.—This ester has, during the past year or two, been recognised as having a most useful odour for modifying flower bouquets. It is a fruity oil boiling at 227° to 228°, and having the constitution... 

The rose odour is still further modified by the presence of the five carbon acid radicle, and judicious blending of the various geranyl esters is capable of giving numerous characteristic bouquets to the various rose odours. This ester boils at 135° to 138° at 10 mm. pressure. 

American perfumers go so far as to state that it has created quite a furore amongst progressive perfumers. It has no distinct flower perfume, and can be used to modify the odour of almost any combination. It is stated that it is so characteristic that nothing can replace it. It is very expensive, but must only be used in minute quantities. 

Uvdecylenic Aldehyde.—This aldehyde is closely related to those just described, but belongs to the unsaturated series. It has the formula CHj CH(CH,3)gCHO. It is very similar to the aldehydes just described, and is used in exactly the same way, namely, for modifying the odour of flower combinations. It melts at -j- 5° to -t- 7° and boils at 118° at 13 mm. 

It is a useful adjunct in the manufacture of perfumes of the carnation type, modifying the odours of eugenol and isoeugenol to some extent. 

It was also notable that the soda treated sludge was always more odorous than the control after only four days, indicating that the effect on odour potential of lime stabilisation is not merely one of altered dissociation equilibria or modified solubilities. 

Within Severn Trent a modified version of this procedure is utilised for the analysis of malodorous emissions. The most significant difference in this approach compared to those already discussed is the use of high resolution gas chromatography in combination with olfactory detection. This method also combines physico-chemical and olfactometric or sensory techniques but in an alternative manner. Utilisation of gas chromatography combined with odour detection is not a new concept and has been employed fairly commonly for the analysis of food aromas, essential oils and other fragrances. The technique is equally applicable to environmental problems and is used frequently in this laboratory for the analysis of atmospheric emissions and taste and odours in water. Three important benefits accrue from this approach in the context of odour emission analysis. 

Figure 4.5. The NP composition of a typical plant extract (in this case, a citrus hybrid) as revealed by gas chromatographic analysis. The peaks on the upper trace represent the different chemicals detected by the instrument, with the peak area being a measure of the amount of any substance. Note that there are a few major NP peaks but even more very minor ones. The spikes pointing down on the lower trace are the odours detected by a human sniffer with their perceived odour name. Note the human detection of odour does not always correspond to the emergence of a major chemical peak. For example near the start of the analysis, the green or burning smell detected by the human does not correspond to any instrument detection so those chemicals are below the level of detection of the instrument. (Modified from the data of Morton M, Smoot JM, Mahattanatawee K, Grosser] and Rouseff RL, Citrus Research and Education Center, University of Florida.)...

One way to prevent the development of unpleasant odours that originate from the decomposition of sweat are antimicrobial finishes or bacteriostatic modified fibres. They prevent the decomposition of perspiration by bacteria to bad smelling products as described in Chapter 15. 

The reaction is catalysed by an organic base, usually an amine, which in the past has nearly always been the tertiary amine 2,4,6-tri(dimethyl aminomethyl) phenol. Such LP-modified epoxy resins have been in existence for more than 30 years. Their popularity declined because of the mercaptan odour of the polysulphide polymers in the uncured state and because of the use of a tertiary aromatic amine. 

Another development that has triggered the revival of liquid polysulphides as modifiers for epoxy resins has been the introduction of polysulphide-epoxy prepolymer compositions which have no mercaptan odour in the uncured state. The manufacture of such compositions involves the co-reaction of epoxy resin in molar excess with a suitable liquid polysulphide in the absence of a catalyst to give ... 

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